There is no easy way to find the Instrument Maintenance assigned to a user, which makes it difficult to change those responsibilities to a different user.  A new tramstop was created that will make it easier to find those scheduled items according to the user that is set up to be assigned for the tasks.  It still requires multiple steps to make the changes, but this will make it much easier to find those that do need changed.

The new tramstop is called SchedulePlanItem List and can be found on the Lab Admin Menu in the Scheduling & Events tramline.

If you go to that page, it will allow you to use the new query, By Assign To that has a User Lookup. 

This search will return all the Schedule Plans with Schedule Plan Items.  I can't go directly to the schedule plan items because of how they're managed in the system, but this will at least get you to where you can find them easier. 

Then clicking on one of the Schedule Plans will take you into where you can manage the Schedule Plan Items, which now has the Assign To column. 

After making the changes here, going back to the list page with the query, you'll see one less entry.  You will need to do this for each and they cannot be modified all at once.